Understanding Batch & Lot Numbers

A batch or lot number is the reference that connects a physical vial to the record of how it was made and tested. This guide explains what the terms mean, why the number matters, and how to use it to find the right documentation.

Batch and lot

The two words are often used interchangeably. U.S. manufacturing regulations, cited here only for their vocabulary, define a batch as a specific quantity of material intended to have uniform character and quality, within specified limits, produced during the same cycle of manufacture. A lot is a batch, or an identified portion of one, with the same uniformity. Products on this site are not drugs, and the regulation is not cited as a standard they meet; its definitions are simply the clearest available.

The key idea is uniformity. Material from one batch is expected to be alike within limits, and that is what allows a test on a sample to describe the batch it came from.

What the number is for

The same regulation describes a lot or batch number as any distinctive combination of letters, numbers or symbols from which the history of a batch can be traced. In practice, the number on a label is how you find:

• the report that covers the material,
• the date the sample was tested,
• the product, form and vial size that were tested.

A number with no record behind it identifies nothing, which is why a useful report prints the batch number it describes.

Reading a batch number

Formats vary between manufacturers. A number may encode a product code, a date or a sequence, or it may be an arbitrary reference. The format itself says nothing about quality. What matters is that the number on the vial and the number on the report are the same.

Matching a vial to its report

• Read the batch number on the vial label.
• Find the report that prints the same number, for the same product and vial size.
• Check the date on the report and the tests it lists.
• Where the report carries a verification reference, use it to confirm the report with the laboratory that issued it.

If the numbers do not match exactly, the report describes different material, however similar the product name.

Why vial size matters

Different fill sizes of the same compound can come from different batches, or be tested as different samples. A report for one vial size does not describe another unless it says so.

Keeping the number with the material

Record the batch number when material is received and keep it with the vial, so the material always ties back to its documentation. Storing & Handling Research Materials sets out a simple record for each vial.

Where this site fits

Where a batch report is published, the COA Library can be searched by batch number, and the product page links the report for the vial size it covers. Why testing is tied to a batch rather than to a product is the subject of Why Batch-Level Testing Matters, and How to Read a Certificate of Analysis shows where the batch number sits on a report.

Sources and references

• 21 CFR 210.3, Definitions. U.S. Code of Federal Regulations, for the terms batch, lot, and lot number, control number or batch number.
• ICH Q6A, Specifications: Test Procedures and Acceptance Criteria for New Drug Substances and New Drug Products: Chemical Substances. International Council for Harmonisation, 1999. Cited for its definitions; its scope is chemical drug substances.
• D. C. Harris, Quantitative Chemical Analysis. W. H. Freeman, on sampling and sample preparation.

Research use

All materials on this site are supplied for laboratory research use only. They are not for human or veterinary use, and this guide gives no instructions for preparing or using them.